Tacrolimus is a macrolide lactone also known as FK506, fugimycin or tsukubaenolide. Tacrolimus is marketed under the tradenames Prograf® and Advagraf® as an immunosuppressive agent to prevent allograft rejection, i.e. rejection of transplanted organs. In the U.S., Prograf® (NDA No. 050708) is approved for the prophylaxis of organ rejection in patients receiving allogeneic liver, kidney, or heart transplants
Advagraf is a once-daily formulation which has not received approval in the U.S. Advagraf failed a non-inferiority study a few years ago as reported in Srinivas et al., Am. J. Transplant 2010; 10: 2571-2573. According to Srinivas,                Although, it has never been definitively determined whether calcineurin inhibitor (CNI) efficacy in general and tacrolimus efficacy in particular is best correlated with AUC, peak or trough, if the AUCs were similar in this study the obvious conclusion would be that the observed efficacy failure [of Advagraf] is most likely related to lower and less frequent peaks with the once a day formulation. Interestingly, in the other phase III trial with once a day tacrolimus, rejection rates were also higher compared to twice a day tacrolimus with equivalent trough levels throughout the study, a further indication that the lower and less frequent tacrolimus peak might be detrimental to efficacy        
Similarly, Barraclough et al., Drugs 2011, 71(12):1561-1577, reported:                Although efficacy of tacrolimus has never been definitively associated with peak or trough concentrations or AUC, an association of peak ciclosporin concentrations with freedom from acute rejection has been demonstrated. This suggests the possibility that the higher rejection rates observed in the previously mentioned studies may be related to the lower and less frequent concentration peaks that are seen with the Advagraf® formulation.        
WO 2005/020993, WO 2005/020994, WO 2008/0145143, WO 2010/005980, and WO 2011/100975 disclose tacrolimus-containing pharmaceutical compositions with improved bioavailability.
There is a continuing need for an improved once-daily tacrolimus regimen which has the same or better efficacy than twice-daily tacrolimus with fewer adverse events.